Pin 4 is high. If there is a PNP transistor that's connected to pins 14 and 4, pull it to see if the amp will power up. This will disable the protection circuit so clamp all transistors, small fuse or limiter....

That's the last component in the protection circuit. Similar amplifiers have thermistors, comparators and other transistors driving that transistor so if that's not the problem, you'll have to follow the circuit back and see what's driving the base of that transistor.